Engine seams

[slusher]

Guys need some opinions, when an engine is on halfs transmission and oil pan you have that seam from oil pan thru the transmission to hide.  I’m struggling to fix it. Would like som advice..

[Mark]

Cement the halves together with liquid cement (not tube glue or CA adhesive).  Sand the seams, paint over with liquid cement, sand again.  Do that a couple of times.

Or, cement the halves together with CA, rout out the seam, then apply two-part epoxy putty or two-part spot putty.  When the part is sanded and ready for primer, you want to see a thin "stripe" of putty where the seam was.

[Force]

I use tube glue for polystyrene models and apply it fairly generously on both sides and let it do it's thing for a minute or two to soften the plastic slightly, then I press the two parts together and let the excess glue and plastic come out of the seam and let it set, after that I brush liquid cement over the seam wich softens both the glue and the plastic and let that dry...then I sand the seam flush and I rarely have to use any putty to hide it.
That's my way of doing it and it has worked for over 40 years.

[espo]

I have tried getting the two halves glued together as evenly as posable. Often there is some "truing" of the mating surfaces before gluing. Seems common for there to be an uneven surface between the two parts even after all this and gluing them together. Usually sanding the two halves after gluing them together and making the oil pan and transmission as even as possible as well as the top of the block under the intake manifold area. The area behind the timing chain cover and water pump is also often an issue. After all of these surfaces are as even as you can get them there will still be a visible line where they meet and often a minor gap. I suggest using whatever you would use on any other problem area on say the body to fill the gaps. In my case I just use some Tamiya Putty, but again whatever you would normally work with should be just fine. Sanding the affected areas after the filler has hardened and then primer to see if the area is smooth enough for you. Can take a couple of applications of filler depending. Then you should be ready for a color coat.   

[yh70]

same as Mark said..

[Shark]

I use tube glue like Force said, I use clamps on it and let it sit overnight.

[Fat Brian]

I agree with using tube glue for engine halves and heads, I like the extra drying time to line things up. Sometimes the alignment pins are misaligned too and that leads to the halves being uneven. I usually trim the pins off and sand the mating face of each half on a long flat sanding stick so I can align them better to save on sanding. Then I sand it with sanding twigs, you can get them on Amazon.

[atomicholiday]

Agreed with what others have said above.

One thing I’ve started doing different lately is fixing the seam on the oil pan, but leaving it on the transmission.  Some 1:1 transmissions have a casting seam, so in my opinion leaving it visible on the plastic is acceptable.  I will usually lightly sand it just to tone it down some, but leaving it visible.

This only applies to the transmission though.  The oil pan will always be fixed.

[maxwell48098]

One thing I always keep in mind regarding engine and trans seams in my 65 years of building is to make sure the seams line up as close as possible, even if it means removing assembly pins or nubs, on the side of the seam that will be exposed in the finished model.  Worry more about visible bottom seams that hidden, top seams.  The use the best liquid cement you have to join the seams.  I'll even push hard on the two halves to make the seam squish a little bit before the cement.

A.J.

[Ulf]

Belive me, it’s my favorite after the glue has set for real. Don’t force, lite and fast over the shape. It follow the shape of oilpan, gearbox etc and the are cheep as our wifes bye them.  I use new one for big seams and a bit used for precision work.

 

[James2]

Hi Carl, my method is simple. I lightly sand both mating surfaces, just enough to flatten the surface and remove the molded in pins. Then I line the parts up as perfectly as possible and clamp them with something like this. When I'm happy with the fit I use liquid cement and an applicator to cement the entire seam. Let is set for a few and then begin sanding, filling and smoothing. I have even used a few dimpling techniques to match the molded in texter of the casting.  I don't spend much time on the areas that can't be seen after final assembly.  

Edited July 24, 2024 by James2

[slusher]

Thank I am reading each post, lots of knowledge on our forum..

[ChrisR]

I glue the halves together with liquid glue. Once dry, Tamiya Light Curing Putty on the joint and sand smooth.

[bobss396]

I always knock the pins off. Then I go with a light application of Tamiya liquid glue, clamp the parts together or hold them in a small vise. After that sets up, I'll give it more liquid glue and let it sit overnight or 2 hours in the dehydrator. Then sand, putty, sand, prime... more putty and sanding if required. It really has to look good from the bottom.

Sometimes I separate the engine and transmission. A little extra work but worth it to paint the parts 2 different colors and look good.

[Street Rod]

I glue the two halves together with tamiya cement, lining both pieces up evenly. Clamp if necessary and let the glue dry for several hours or overnight. Then I use a small fine flat file to flatten the seams, including the front and top seams, followed by 600 grit sandpaper to smooth everything down, lightly with 400 grit if necessary. Also filling any sink marks, etc. Prime the engine and sand the areas that show when the model is complete, then paint with the color of choice.

The pictures below show the engine for my current project and a painted an complete engine in a finished build that had a seam down the center of the engine/trans.

 

[TransAmMike]

The liquid glue seems (ha, no pun intended...well maybe?) to work pretty good for me.  As has said, be sure the mating surfaces have been sanded flat after removing the pins.

[Ace-Garageguy]

1 hour ago, TransAmMike said:

The liquid glue seems (ha, no pun intended...well maybe?) to work pretty good for me.  As has said, be sure the mating surfaces have been sanded flat after removing the pins.

Yup.

And sometimes a light application of filler is necessary...and I ALWAYS prime and sand and re-prime until every unwanted seam is entirely gone.